1. Field of the Invention
The present invention relates to the technical field of liquid crystal displays, and in particular to a liquid crystal panel and a driving method thereof, and also relates to a liquid crystal display comprising the liquid crystal panel.
2. The Related Arts
A liquid crystal display (LCD) is a flat and ultra-thin display device, which is composed of a predetermined number of color or monochromic pixels to be placed in front of a light source or a reflection surface. The liquid crystal display has extremely low power consumption and possesses various advantages, such as high image quality, small volume, and light weight, and are thus very favorite by the public, making it the mainstream of display devices. The liquid crystal displays that are currently available are primarily thin-film transistor (TFT) liquid crystal displays. A liquid crystal panel is a major component of the liquid crystal display.
FIG. 1 is a schematic view showing the structure of a conventional liquid crystal panel. As shown in FIG. 1, the liquid crystal panel comprises a display area 1 comprising an array of pixel units px arranged therein, a source controller 2, a gate controller 3, a gamma voltage control section 4, and a chamfer voltage control section 5, wherein the chamfer voltage control section 5 supplies a chamfer voltage to the gate controller 4 to allow the gate controller 4 to generate a corresponding scan signal supplied to the pixel units px. The gamma voltage control section 3 supply a gamma voltage to the source controller 2 to allow the source controller 2 to generate a corresponding data signal supplied to the pixel units px. The pixel units px of the liquid crystal panel comprises a thin-film transistor and an equivalent circuit diagram of a pixel unit px is illustrated in FIG. 2. As shown in FIG. 2, in the drawing, Vgh indicates a turn-on voltage that the gate controller 4 supplies to the thin-film transistor; Vgl indicates a turn-off voltage that the gate controller 4 supplies to the thin-film transistor; Cgs indicates a parasitic capacitor; Cst indicates a storage capacitor; and Ccl indicates a liquid crystal capacitor. Due to the existence of the parasitic capacitor Cgs, repeatedly turning on and off the thin-film transistor leads to the generation of a feed-through voltage ΔV, wherein ΔV=(Vgh−Vgl)Cgs/(Cgs+Ccl+Cst). The existence of ΔV affects the displaying quality of the liquid crystal panel, such as generating a flicker phenomenon. The liquid crystal panel discussed above uses the chamfer voltage control section 5 to generate a chamfer voltage supplied to the gate controller 4 and the scan signal supplied from the gate controller 4 to the thin-film transistor has a waveform illustrated in FIG. 3. By decreasing the difference between the turn-on voltage Vgh and the turn-off voltage Vgl, the purpose of reducing ΔV may be achieved.
In the liquid crystal panel provided above, the chamfer voltage control section 5 supplies a fixed chamfer voltage. In other words, the difference between the turn-on voltage Vgh and the turn-off voltage Vgl is set constant for image signals of different grey levels. However, for different grey levels, the liquid crystal capacitor Clc is different and ΔV increases with the increase of the grey level. The relationship between ΔV and grey level is illustrated in FIG. 4. The greater the difference of ΔV between high and low grey levels is, the more unbalanced the common voltage Vcom of the pixel unit px will be and the worse the displaying performance of the liquid crystal panel will be.